Geochemical evolution and petrogenesis of the eocene Kashmar granitoid rocks, NE Iran: implications for fractional crystallization and crustal contamination processes

Abstract

Kashmar granitoids of Taknar zone, in north part of Lut block, intruded into volcanic rocks and consist of granites, granodiorites, monzodiorite and gabbrodiorites. They are composed of mainly plagioclase, alkali-feldspar, quartz, amphibole, biotite and pyroxene minerals. Harker diagram variation, including negative correlations CaO, MgO, FeO, TiO₂ and V and positive correlations K₂O, Rb, Ba, and Th, with increasing SiO₂ and chondrite-normalized REE patterns, suggest that fractional crystallization of gabbrodioritic rocks could have played a significant role in the formation of granites. Their chondrite-normalized REE patterns are characterized by LREE enrichment and show slight negative Eu anomalies. Chondrite-normalized REE modelling indicates that the magma of Kashmar gabbrodiorites were generated with 3–5% of partial melting of a a spinel-lherzolite source. Melting of parental magma located at ~53 km.